The present invention relates to an improved filter, particularly of the type which is installed in aquariums and buried under sand or gravel.
Each of these filters is in practice constituted by one or more plates which are provided with a plurality of slots and are arranged side by side on the bottom of an aquarium so as to form an interspace by virtue of the presence of lower protrusions with which they are provided.
Said plates, which are preferably made of plastic material or of another material which does not degrade in the course of time, are then covered by a layer of gravel, sand or other material, and a recirculation pump is connected to a hole of a plate by means of a suction tube and thus draws the water from the bottom, filtering it through the sand and recirculating it in the upper part.
The suction tube is generally arranged in a corner of the aquarium, and since current commercially available plates are in practice constituted by a uniform filtration grid, water is drawn where it encounters less resistance and thus in a very small region which is adjacent to the suction tube.
This naturally negatively affects the operation of the filter, and thus water recirculation occurs only in small regions of the aquarium.
Further negative effects occur due to the deposition of impurities confined at the regions adjacent to the suction tube.